Color vision deficiency (CVD), also commonly called color blindness, refers to a limited ability of some individuals to perceive differences between certain colors. CVD is caused by a lack or a deficiency of one or more color photoreceptors in the human eye. Such color photoreceptors are of three types: long wavelength (L), medium wavelength (M), and short wavelength (S) cones, which are sensitive to the red, green, and blue portions of the visible spectrum, respectively. Approximately 7-10% of males and 0.5-1% of females are color vision deficient to some degree. Red/green color blindness is the most common form of CVD.